I sold real estate for a 3-4 year period and our current real estate laws from state to state are pretty much the same (with sublte nuances smattered about) and the bulk of these laws originate from English law.
That being said, any person can be a landowner despite their age. Those under that age regarded as being an adult must have a gardian who handles that persons affairs Ad Litium (I think that's how it's spelled) being directed through the courts.
My sister-in-law passed away from breast cancer many years ago and she had taken out a life insurance policy for my then 10 year old son. My wife and I had to prove to the court that we were married, of sound judgement and we could manage not only our affairs but this windfall of money that a 10 year old now owned. Any decision we made had to have the approval of a sitting judge and the wife and I were required to report once a year to a judge to discuss any future plans, intentions, so forth and so on.
I would guess that persons in the 1700's could indeed hold land (inheratence, estates, whatever), but it would most likely be administered by a gaurdian. This is pointed out in Ambrose's book Undaunted Courage, concerning Merriwether Lewis, who at a young age inherited a wide expance of property, chattels, and slaves.
Just some thoughts and observations....